The Great Megapixel Debate

Your personal digital camera gives you a six megapixel image. Your teenage daughter’s cell phone captures two megapixel photos. Why are you satisfied that the camera in your surveillance system is limited to 0.3 megapixels (at 4CIF)? Chances are that your DVR is programmed to capture only a quarter (CIF) of the camera’s maximum resolution (4CIF) to provide a paltry .075 megapixels?
It doesn’t have to be that way. With megapixel camera sales doubling year after year, more manufacturers are providing a broad set of products for both indoor and outdoor applications. As IP cameras are becoming more commonplace for security applications, end-users are taking advantage of the megapixel resolutions to improve image quality, reduce the number of cameras and to provide better overall situational awareness.

Manufacturers
IQinvision, San Juan Capistrano, Calif., and Arecont Vision, Glendale, Calif., have established themselves as leaders in megapixel camera products for security. Until recently, megapixel cameras were considered a niche product in the growing IP camera market. As IP camera solutions have become more commonplace, upstarts like Avigilon, Vancouver, B.C., have entered the market as well as established camera providers such as Axis, Bosch and Sony. The cost of a 1.3 megapixel camera starts as low as $500 suggested retail. Several manufacturers state a strategy to aggressively price their cameras to compare favorably with name brand analog cameras.
Most megapixel products use Motion JPEG (MJPEG) compression. Like standard resolution IP cameras, MPEG-4 and H.264 products are beginning to surface on the market.

Management software
Like any network camera, megapixel units are typically managed with video management software (VMS). Most camera manufacturers provide a basic video management and recording solution. Many manufacturers also partner with open software solutions such as Genetec and Milestone.

To date, many VMS systems have typically treated megapixel cameras like most standard resolutions network cameras and have not integrated key features that are unique to megapixel cameras:
Image cropping modifies the aspect ratio from the traditional 4:3 to 16:9. This offers better viewing for security video which often has more interest in the horizontal direction. Image cropping optimizes each scene by clipping the image to eliminate unwanted, wasted video to save bandwidth and storage.

Digital pan-tilt-zoom (PTZ) control allows the user to virtually move around and zoom into an image using a smaller viewing window. The system still records the entire image since movement is virtual.

Analog standards are limited
The analog video standards (NTSC) that have defined North American CCTV since the 1950s limit video resolution to 640 x 480 pixels (4CIF). This equates to an overall image resolution of about 0.3 megapixels. Digital cameras are not bound by the NTSC resolution standards. While the majority of the network cameras sold each year are limited to standard resolutions, camera sales of 1.3, 2 and 5 megapixel are growing by at least 100 percent each year.
The major criticism of megapixel cameras is the large data rate that can be generated to consume precious network bandwidth and disk storage. The increased resolution puts additional performance demands on both the camera and the overall surveillance system.

Reducing the number of cameras
Paul Bodell, vice president of Sales and Marketing at IQinvision called the bandwidth problem a “myth” because it’s usually not viewed in the proper context. Bodell said that it’s wrong to compare the data rate of a single megapixel camera with a standard-resolution camera.

The value proposition for many megapixel camera purchases is the reduction of the number of cameras required to provide surveillance coverage. Megapixel cameras can cover a much larger viewing area versus NTSC resolution cameras, reducing the total camera and installation cost of a surveillance system. Bodell surmised that in some situations a 1.3 megapixel camera could replace six or seven analog cameras while providing equivalent coverage.
The most common applications are outdoor spaces (parking lots, public transportation areas) that involve wide areas. Bodel estimated that over 80 percent of IQinvision cameras are used in outdoor applications. IQinvision has over 19 camera products, many of which are designed for outdoor use. Models include mini domes, all-weather systems and cameras with day/night capabilities.

In addition to camera reduction and overall better video quality, Dave Tynan, vice president of Sales and Marketing at Avigilon noted that a megapixel camera system offers improved situational awareness. “With conventional surveillance systems and pan-tilt-zoom cameras, security professionals have to make a choice between seeing the whole parking lot, situational awareness, or a single license plate-- the detail. But they can’t see both at the same time.” After an incident, if the PTZ camera was not positioned on the right detail, the incident is not recorded. With digital PTZ, the megapixel system is able to deliver both situation awareness and detail at the same time.
Unlike a traditional PTZ camera that ignores the bigger scene while in a zoom mode, the megapixel system can continue to provide live images of the full scene while providing a zoom image of a detail. Likewise, the digital PTZ features can be used in playback mode to provide a close forensic review of an incident without sacrificing quality.

Tools for surveillance design
IQinvision and Avigilon as well as others provide installers with calculator tools to determine how many cameras are needed to adequately cover a given horizontal area at a desired video quality. The idea is to apply the required number of pixels to the application. For example, to reliably recognize a license plate requires 50 pixels per foot whereas a face requires 90 pixels. IQinvision’s calculator helps the installer calculate how many frames per second should be captured to match the speed of an object (car versus people).

Tom Galvin of NetVideo Consulting is a network video specialist. His Web site is www.netvideoconsulting.com.

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